The road surface friction coefficient μ is a time varying characteristic that can deviate widely in a short time, especially for a vehicle running at a high speed. In order to optimize a vehicle stability control system, it is desirable to know the road surface friction coefficient μ during vehicle operation. Using this information the control system can change yaw control parameters for different types of road surfaces (asphalt, gravel, snow, ice, and etc.) to help optimize the stability control system response. Currently there is no method to directly measure the coefficient μ; it therefore must be estimated by the control system using sensor information that is available on a vehicle.